Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with transitional graphical user interface showing our new design;

FIG. 2 is a front view of a second image thereof;

FIG. 3 is a front view of third image thereof; and,

FIG. 4 is a front view of fourth image thereof.

The broken line(s) on the display screen, text, and images form no part of the claimed design. The appearance of animated images sequentially transitions between the images shown in FIGS. 1-4. The process or period in which one image transitions to another forms no part of the claimed design. 

CLAIM We claim the ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 